Researchers reveal how an insectivorous plant uses energy from rain to power its traps

Scientists at the University of Bristol have discovered the deadly workings of a carnivorous plant.

In the steaming jungles of Borneo, plants have developed countless tricks to help them survive and outperform their neighbors. The slender pitcher plant, Nepenthes gracilis, is among the most ingenious: its elaborate cup-shaped leaves are fitted with a canopy-like hanging lid that turns into a deadly springboard for ants when struck by a drop of rain.

The results, published today in Biology Letters, reveal for the first time how the deadly supply works.

The team was surprised to find that, rather than bending into the lid itself or the narrow constriction between the pitcher cup and the lid, the spring is located far to the rear of the tubular wall of the pitcher. The off-center location at the back of the tube has two effects.

First, it makes the spring dependent on the way and therefore the cover moves easily down, but not up. When a raindrop hits, the lid is quickly accelerated downward, sending any insects sitting on its lower face back into the liquid-filled trap below. However, on the way up, the increased resistance of the spring slows the lid down, so it stops moving sooner and the trap is quickly ready to capture again.

Second , the off-center spring prevents the lid from twisting or wobbling, maximizing the transmission of impact energy in the downward motion.

Lead author Anne – Kristin Lenz from Bristol’s School of Biological Sciences explained: “If you look at the shape of the pitcher, you would assume that the deformation is occurring at the smallest cross-sectional portion, which is the transition point from the lid to the tube of the pitcher , but in fact it also deforms further down the back of the launcher tube.

β€œThe pitcher plant traps are lightweight, yet sturdy. Nepenthes gracilis uses small changes in the shape of the trap to transmit impact energy with astonishing efficiency. We can learn from these plants how to geometrically optimize constructions, which could help save material and weight, while having a functional spring. The springboard’s trapping mechanism could even inspire the design of new mechanical devices to harvest energy from rain or hail.

This clever use of geometry makes Nepenthes gracilis the only plant known to harness an external source of energy to achieve extremely rapid movement – ​​entirely free of metabolic costs.

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